| Abstract: | The intracellular Na and K concentrations (Na]i, K]i) of extensor digitrum longus (EDL) and soleus (SOL) muscles of 3- to 52-week-old rats were estimated flame-photometrically. The extracellular space of 3-week-old rat muscles was significantly greater than that of 15-week-old rat muscles. The K]i of the both muscles decreased gradually with age while Na]i remained nearly constant. EDL had higher K]i and lower Na]i than SOL and the sum of the concentrations of K]i and Na]i was significantly greater in EDL than in SOL throughout the age period tested. Significant measurement errors were found in muscles from the youngest age group, where samples weighed less than 50 mg. A method for calculation of corrected Na]i and K]i values is discussed. |
